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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e3eaf5380e3048e7dd6153bf77e91ef237d0aaf47104c0dd4be1e0f2e96f06' 
  AND token = 'RgTrPBaGyScQHSqOTryWW85XRGx8dPAaDqZgMubZUgo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}