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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75ebd55d903c09e7736cbccfe0d58582c7173ce68d9cbbc14a8871be37755fbd' 
  AND token = 'bF/mg0hc6fvO9jdMsRt3WZCtC4/Iy+MAEf4KTRiiu7g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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